One example of such a dispensing device is a needleless injector. Needleless injectors of various types are described in, inter alia, International Patent Publications Nos. WO 93/03779 and WO 95/03844, which are in the name of the present applicant. The present invention will be described in detail with reference to a needleless injector, but it is to be understood that it applies to other types of spring powered dispensing device also.
In a spring powered needleless injector of the type described in the above International Patent Publications, the spring continuously exerts a force on a dispensing member, prior to use, and restraining means are provided for preventing the dispensing member moving under the force of the spring. The needleless injector is fired by, in effect, moving the injector into a condition in which the restraining means no longer have a restraining effect, thus permitting the dispensing member to move.
There is, however, a potential problem is assembling such devices, in that if the device is to be easily operable by the user, it may be easy, or at least possible, for the device to be accidentally fired during the process of manufacture. This is not only wasteful, but also poses a safety hazard to the personnel involved. It is an object of the present invention to provide means for overcoming this problem.